linux-kernel - Re: [PATCH v3 13/28] slub: create duplicate cache

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Message-ID: <4FC506E6.8030108@parallels.com>
Date:	Tue, 29 May 2012 21:27:02 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	<linux-kernel@...r.kernel.org>, <cgroups@...r.kernel.org>,
	<linux-mm@...ck.org>, <kamezawa.hiroyu@...fujitsu.com>,
	Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
	Greg Thelen <gthelen@...gle.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>, <devel@...nvz.org>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH v3 13/28] slub: create duplicate cache

On 05/29/2012 09:25 PM, Christoph Lameter wrote:
>> I will try to at least have the page accounting done in a consistent way. How
>> >  about that?
> Ok. What do you mean by "consistent"? Since objects and pages can be used
> in a shared way and since accounting in many areas of the kernel is
> intentional fuzzy to avoid performance issues there is not that much of a
> requirement for accuracy. We have problems even just defining what the
> exact set of pages belonging to a task/process is.
>
I mean consistent between allocators, done in a shared place.
Note that what we do here *is* still fuzzy to some degree. We can have a 
level of sharing, and always account to the first one to touch, we don't 
go worrying about this because that would be hell. We also don't
carry a process' objects around when we send it to a different cgroup. 
Those are all already simplications for performance and simplicity sake.

But we really need a page to be filled with objects from the same 
cgroup, and the non-shared objects to be accounted to the right place.

Otherwise, I don't think we can meet even the lighter of isolation 
guarantees.

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